U.S. Pat. No. 5,103,367, entitled Electrostatic Chuck Using AC Field Excitation relates to a mechanism for holding semiconductor wafers in contact with a support during treatment of the wafers. The '367 patent discloses three electrodes, two of which define a substantially planar surface and are embedded within a thin dielectric film. These two electrodes are excited by a low-frequency AC supply to produce sine wave fields of controlled amplitude and phase. The third electrode provides a reference point for the other two electrodes. By controlled rates of voltage application and removal, low-voltage gradients are obtained on the wafer support. This results in no retentive forces between the dielectric medium and the wafer. A low alternating current amplitude excitation of the chuck enables capacitative current sensing of the relative positions of the wafers and the dielectric film enabling simple control of voltage application to the electrodes.